Non-invasive techniques, typically using ultrasound, are well-known for determining bladder volume, i.e. the amount of urine in the bladder. The reliability and accuracy of such ultrasound techniques have been well-documented and they are now well accepted by the medical community. Information concerning bladder volume is used by health professionals in the treatment of bladder dysfunction and to prevent over-filling of the bladder in those cases where there is a permanent or temporary loss of bladder sensation, due to spinal cord injuries and/or postoperative recovery, as well as other reasons.
It is also well-recognized that an important aspect of good bladder health involves prevention of bladder distension. Typically, as bladder pressure increases, due to increase in volume of urine, ultimately leading to the point where bladder distension begins to occur, incontinent episodes will occur because the sphincter muscles are unable to retain the urine in the bladder. On many individuals, the point of incontinence occurs consistently at a particular volume. If this particular volume is known, then incontinent events can be prevented by using information on bladder pressure/distension.
If the bladder continues to fill so that it becomes hyperdistended, renal damage, renal failure and in some cases even death can occur. Hyperdistension, like distension, can be successfully prevented, however, by measuring using bladder distension.
At low bladder volumes, bladder distension information is typically not very useful. As the bladder fills, however, a quantization of bladder distension becomes more useful relative to ascertaining problematic conditions. Bladder distension information is potentially more useful than just straight volume measurements because normal bladder capacity varies widely across the human population. The same volume of urine in two different patients can have very different consequences.
There have been previous attempts to quantize bladder distension, including the use of ultrasound back wall scatter characterization in determining bladder wall thickness. Bladder wall muscles will stretch and thin as the bladder fills. This thinning of the bladder wall can be directly measured by recording backscatter information at various known volumes for a particular patient. Such methods, however, are not particularly reliable or consistent and often do not directly correlate with actual distension of the bladder.
In the present invention, a substantially different approach is taken, directed toward ascertaining the degree of roundness of the bladder as it fills, with increasing roundness being a reliable indication of pressure.